Lubricating oil



Patented Nov. 3, 1936 PATENT OFFICE LUBRICATING OIL Edwin J. Barth, Chicago, Ill., and Ralph P.- Curlew, Hammond, Ind., assignors to Sinclair Refining Company, New York, N. Y., a corporation of Maine No Drawing. Application June 11, 1935, Serial No. 26,038

1 Claim.

This invention relates to improvements in lubricating oils and, more particularly, relates to compounding materials, so-called pour depressors", for lowering the pour point of wax-containing lubricating oils, of petroleum origin for example. Various materials have been found to depress the pour point, the temperature at which wax-containing lubricating oils cease to flow, under definitely specified conditions in the conventional pour test, when added to the lubricating oils in proportions varying from a fractionof 1% toa few per cent. (by weight) on the oil. Some of these pour depressors have been useful for this purpose only under special conditions, many have impaired other qualities of the oil while depressing the pour point and most of those of reasonably general application have been expensive. This invention provides new pour depressors which are generally useful, which do not impair most of the usually required qualities of lubricating oils and which are of low cost.

The pour depressors of this invention are the aluminum salts of the organic acids produced by oxidation of paraflin wax, the so-called wax acids. These wax acids have acid numbers approximating 120 or higher, saponification numhers approximating 130 or higher and molecular weights in the general neighborhood of 400. The aluminum salts of these acids are excellent pour depressors and enjoy a combination of important advantages.

These wax acids can be produced by oxidation of paraffin wax in accordance with conventional practices, for example by blowing with air or other oxygen-containing gas or by reaction with cerium sulfate. Oxidation by blowing with air or the like is, however, advantageously effected at relatively low temperatures, temperatures in the neighborhood of 250 F. for example. The oxidation may be carried out with or without the use of oxidation catalysts. The wax acids so produced by oxidation of paraffin wax may be separated from any unreacted or incompletely reacted wax and converted to the aluminum salts in accordance with conventional practices. following method of preparation of the aluminum salts of these wax acids, the pour depressors of this invention, has been found particularly advantageous:

Three kilograms of paraflin wax having a melting point of 130-132 F. are charged into a 5 1 liter flask equipped with a stirrer and a tube for introducing air into the charge in the flask. 60

The

the flask to 230 F., air preheated to 230 F. is blown through the charge, in the flask at a rate of 10 cubic feet per hour while maintaining the charge in the flask at a temperature of 230 F. The blowing is continued until the acid number of the charge in the flask approximates 10, about 40 hours for example. The blowing is then stopped and the charge in the flask cooled. The

wax acids are extracted from the charge in the flask with about 3 kilograms of isopropyl alcohol and the alcohol is distilled from the extract to recover a wax acid product. This product should be of good color, white, should contain upwards of 75% saponifiable material and should represent about 40% by weight of the wax subjected to the oxidation. Although the oxidation can be continued, in the manner described, until the charge in the flask has an acid number as high as or higher than "70, the efiiciency of the oxidation, with respect to time, decreases after an acid number of about 40 is reached. Unreacted wax, together with added make-up wax, can be resubjected to the oxidation operation. This wax acid product is saponified by heating for 1 hour at 170 F. with a 5% aqueous solution of sodium hydroxide in proportion containing that amount of sodium hydroxide theoretically required to react with the wax acids. The temperature of the solution is then raised to 190 F. and maintained at 190 F. for 30 minutes. The supernatant layer of unsaponifiable matter is thereafter decanted from the aqueous solution of the sodium salts of the wax acids. This soap solution is diluted with an equal weight of water and, after being brought to a temperature of 170 F., is reacted with an amount of aluminum nitrate somewhat exceeding that theoretically required to react with the sodium salts of the wax acids. The thus precipitated aluminum salts of the wax acids are coagulated by heating, in the presence of the resulting solution, to a temperature of 190 F., maintained for 30 minutes. This aluminum soap is filtered from the solution and washed with twice its weight of water. This washing should be thorough to insure removal of water soluble salts. Following washing, the aluminum soap is dried, at a temperature of 150 F. under a vacuum for 16 hours for example. To remove any traces of oil-insoluble salts, this aluminum soap is dissolved in an equal weight of benzol, the benzol solution thoroughly washed with water and, after separation of water, the benzol is distilled from the aluminum soap at a temperature not exceeding 250 F., under a vacuum corresponding to 5 mm. of mercury absolute for example. The resulting product, the aluminum salts of the wax acids, should be of light tan color. Other aluminum salts, such as aluminum sulfate, can be substituted for aluminum nitrate in the foregoing procedure. The wax acids produced by the oxidation can also be saponified with sodium hydroxide in the presence of unreacted wax, thus eliminating the extraction of the wax acids with isopropyl alcohol. This method can be applied to paraifln waxes of higher and of lower melting point than that 01 the wax specifically mentioned.

Used in a proportion of 1% on the oil, the pour depressors of this invention, such as those produced by the method of preparation Just described, effeot reductions in the pour point, as conventionally determined, 0! as much as F. or more, and used in proportions of as little as 0.25% on the oil these pour depressors efiect reductions oi as much as 20 F. or more. The following illustrations oi. lubricating oils embodying the invention, that is including the pour depressors of the invention, will illustrate the application of these pour depressors and their eiIect in lowering the pour point:

1. The pour depressor of this invention, prepared as just described, was added to a Mid-Continent lubricating oil, S. A. E. 20, dewaxed to a pour test of 0 F. in amounts of 0.13% and 0.25%. The pour test of the lubricating oils including the pour depressor was --20 F. in each instance.

2. This pour depressor was added to a Mid- Continent lubricating oil, S. A. E. 40, which had not been dewaxed and which had a pour test of 45 F., this lubricating oil including an undewaxed but acid treated Mid-Continent long residuum having a pour test of F., in amounts of 0.25%, 0.50%, 1.0% and 2.0%. The pour tests of the lubricating oils including the pour depressor were 10 F., 15 F., 20 F., and --20 F., respectively.

3. This pour depressor was added to a Pennsylvania lubricating 011, S. A. E. 40, dewaxed to a pour test of 20 F., in amounts of 0.25%, 0.50%, 1.0%, 1.5% and 2.0%, pour tests of the lubricating oils including the pour depressor were +5 F., 0 F., -10 F., 15 F. and -15 F., respectively.

4. This pour depressor was added to a Pennsylvania lubricating oil having a viscosity of 120 seconds at 210" F., Saybolt, and a pour test of 90 F., in amount oi 2.0% on the oil to produce a lubricating oil having a pour test of 55 1".

The pour depressors of this invention have the necessary solubility in oil. They are highly eiiective and need be used in but small proportion with respect to the oil. In proportions up to about 2% (by weight) on the 011 they do not noticeably afiect the color oi! the compounded product and even in higher proportions they affect the color very little. Compounded products including the pour depressors oi the invention are as stable as the lubricating oil to which the pour depressor is added, remain as clear and bright and have no increased tendency to deposit wax or sludge. Addition of these pour depressors does not increase the rate oi oxidation of the lubricating oil and does not involve any tendency toward decomposition. The pour depressors 01 this invention remain efiective as pour depressors at elevated temperatures and over prolonged periods. Compounded products including these pour depressors are no less stable as to color. with respect to temperature and with respect to time, than the lubricating oil itself. In proportions up to 2% on the oil, addition of the pour depressors of this invention does not materially increase the Conradson carbon content of the compounded product. Acid numbers of compounded products including the pour depressors oi the invention are low. The viscosity index of the lubricating oil is not adversely affected by the addition of the pour depressors of this invention. The pour depressors 0! this invention, moreover, appear to be of special utility in the heavier and the more viscous lubricating oils, in Pennsylvania lubricating oils having viscosities upwards of seconds at 210 F. for example.

We claim:

A wax-containing lubricating 011 including, as a pour depressor, an aluminum salt oi. the organic acids produced by oxidation of paraflin wax.

EDWIN J. EARTH. RALPH P. CORLEW. 

